please help --xiaobaitu

thanks in advance xiaobaitu;
I have been filed I140(Eb1b and NIW)and I485 on April, 2005. Both my I140 have been approved . Now I want to change my job. My I485 was attached to my Eb1b. My question is : should I change my I 485 to my NIW before changing my job? is there any influence to my I485 if I change my job? Can I do it successfully to change my I 485 to my NIW? thank you so much! I am waiting on line.